108 GEOLOGICAL MEMOIRS. 



Of the Bivalves, the greater number of the Red Sea species 

 belong to the division unimusculosa. 



6. Comparison of the Fauna of the Sechelle and Admiralty 

 Islands ivith that of South Italy. 



M. Dufo has given (in the Ann. des Sc. Nat. 2d Ser. vol. xiv. 

 for 1840.) a list of the mollusca of these islands, enumerating 276 

 species, namely, 220 conchiferous marine gasteropoda, 1 1 land gas- 

 teropoda, 2 fresh-water gasteropoda, and 43 marine bivalves. Since 

 the smaller species throughout, and all the cephalopoda, pteropoda, 

 brachiopoda, and naked gasteropoda are omitted, this catalogue 

 can of course give but a very imperfect view of the fauna, but 

 notwithstanding this I have thought it better to bring it within 

 the sphere of my observations. Of the 276 species, we find the 

 following nine in the Mediterranean : — 



Modiola lithophaga L. Cypraea annulus L. 

 Lima squamosa Lam. moneta L. 



Bulla ampulla L. helvola L. 



Ianthina fragilis Lam. Dolium Galea L. 

 Tornatella tornatilis L. 



But of these the Bulla ampulla and all the Cyprsese belong to 

 the very rarest of the mollusca, indigenous in the Mediterranean, 

 and they must even be considered doubtful. 



7. Comparison of the Fauna of the United States with that of 



South Italy. 



It is unquestionably a very important point to discover how far 

 the Atlantic Sea, as it separates the Flora and Fauna of the land, 

 nourishes different mollusca on its eastern and western shores. 

 Unfortunately, however, I have found it impossible to obtain even 

 the most necessary materials for such comparison. 



My only authorities have been the " Journal of the Academy of 

 Natural Sciences of Philadelphia," vols. i. ii. and v. ; and " Say's 

 American Conchology," as far as plate 50. The American edition 

 of Nicholson's Encyclopaedia and the remaining volumes of the 

 Philadelphian Journal I have not been able to obtain ; and, un- 

 luckily, the collections of shells which I have received from my 

 North American friends, Messrs. Lee, Morris, and Griffith, are very 

 poor in marine species. The following European species are, how- 

 ever, found in the United States : — 



*Mya arenaria L. (M. mercenaria Say) 



Scrobicularia piperata Gm. (Amphidesma transversum Say) 



*Cyprina islandica L. 



Achatina lubrica L. 



Helix fulva Mull. (H. chersina Say) 



pulchelia Mull. (H. minuta Say) 

 *Paludina vivipara L. 

 porata Say 



